1 Field of the Invention
This invention relates to an elastic knitted fabric including an elastic yarn and able to be used for innerwear, outerwear, sportwear, an industrial material or the like.
2. Description of the Related Art
An elastic warp knitted fabric including an elastic yarn such as a urethane elastic yarn, an elastic textured yarn or the like has a broad application due to a superior elongation, elastic recovery and tightening force thereof up to now. For innerwear, a sufficient elongation, elastic recovery and tightening force are required, to adjust to a figure of a human body and protect the human body from unnecessary vibration generated by body movement. In sportwear, an optimum elongation, elastic recovery and tightening force, which do not obstruct a free movement of the human body, are required, and thus the elastic warp knitted fabric including the elastic yarn such as the urethane elastic yarn, the elastic textured yarn or the like has been used for almost all applications.
Nevertheless, although a conventional elastic warp knitted fabric has a superior stretchability in a wale direction, there is no warp knitted fabric having a superior balance between an elongation in a wale direction and an elongation in a course direction, i.e., the warp knitted fabric having a ratio between the elongation in the wale direction and the elongation in the course direction which is near to 1, and thus when clothing is made from the conventional warp knitted fabric, a cutting direction of the warp knitted fabric must be taken into consideration.
Japanese Unexamined Patent Publication (Kokai) No. 60-224847 and Japanese Unexamined Utility Model Publication No. 51-88682 disclose elastic warp knitted fabric having the same knitting weave, i.e., one weave of a satin net, as that of the warp knitted fabric in accordance with the present invention, but there is no description of a shape of a sinker loop of the elastic knitted fabric in the above two publications, and it is well known that a shape of the sinker loop largely depends on a type of dyeing and finishing process used. Further, there is no description of a type of dyeing and finishing process used for the elastic warp knitted fabrics, in the two above publications.
A conventional dyeing and finishing process of a common elastic warp knitted fabric has been disclosed, for example, in Japanese Unexamined Patent Publications (Kokai) No. 61-174458 and No. 60-224847. Namely, Japanese Unexamined Patent Publication (Kokai) No. 61-174458 discloses that a relaxation treatment, a dehydration treatment, a preset treatment, a scouring and bleaching process, a warm water rinsing treatment, a dyeing treatment, warm water rinsing treatment and a finishing set treatment are sequentially applied to an elastic warp knitted fabric in which an elastic yarn is inserted. The Japanese Unexamined Patent Publication (Kokai) No. 60-224847 discloses a dyeing and finishing process using the above-described sequential treatments in which a preset treatment and a finishing set treatment of the temperature of 170.degree. C. or more, preferably between 180.degree. C. and 200.degree. C., are applied to the elastic warp knitted fabric under a stretching treatment in the wale and course directions. Nevertheless, the ratio between the wale elongation and the course elongation of the elastic warp knitted fabric obtained becomes 2 or more, as described, for example in Japan Research Association for Textile End-Uses Vol. 27, No. 1, 1986. Accordingly, when clothing is made from the conventional elastic warp knitted fabric, it is necessary to select as suitable cutting direction due to an inferior balance between the wale elongation and the course elongation. As can be clarified in the above description of the prior art, the sinker loops are set to a stretched state in the elastic warp knitted fabric having an inferior balance between the wale elongation and the course elongation, and thus a density of yarns constituting the knitted fabric becomes coarse.
Namely, a sinker loop of a nonelastic yarn binding two adjacent elastic yarns is formed from a needle loop side of an elastic yarn to a needle loop side of another adjacent elastic yarn, or from a sinker loop side of an elastic yarn to a needle loop side of another adjacent elastic yarn in a power net. After an application of the dyeing and finishing process, the sinker loop formed by the nonelastic yarn is stretched, and thus a knitted fabric becomes coarse because a distance between the two adjacent elastic yarns is widened. In this state, i.e., a state that an angle .theta. of the sinker loop defined by a method described in detail later is less than 48.degree. , even if this knitted fabric is stretched, the knitted fabric does not have enough elongation to be stretched, and thus a knitted fabric having only a lower elongation is obtained. This feature may appear strongly in the course direction of the knitted fabric.
The above described matter teaches that an elastic warp knitted fabric having a superior balance between the wale elongation and the course elongation is a warp knitted fabric having an elongation sufficient to be stretched in the course direction, and it is necessary that the sinker loop formed by the nonelastic yarn has a bulge shape.
The bulge shape of the sinker loop formed by the nonelastic yarn is generally kept in the grey fabric, but the bulge shape of the sinker loop is eliminated by a tension applied in a course direction in the dyeing treatment or by a force used for applying a set in a wale direction, to provide a dimensional stability to the knitted fabric and to prevent creases generated in the dyeing process
When the dyeing and finishing treatments are applied to a satin net, a sinker loop of a nonelastic yarn binding two adjacent elastic yarns in a sinker loop side thereof is also stretched, i.e., a radius of curvature of the sinker loop of the nonelastic yarn and defined by a method described in detail later is infinity, a distance between two adjacent elastic yarns is widened, and a density of the knitted fabric becomes coarse. Nevertheless, the sinker loop formed by the nonelastic yarn in a grey fabric of the satin net has essentially a bulge shape, and a balance between the wale elongation and the course elongation of this knitted fabric is superior.
Consequently, the sinker loop formed by the nonelastic yarn in a grey fabric of the elastic warp knitted fabric has essentially a bulge shape and the knitted fabric has a superior balance between the wale elongation and the course elongation. Namely, in a state of a grey fabric, the nonelastic yarn has an angle .theta. of a sinker loop larger than 48.degree. in the power net, and a radius A of curvature of sinker loop of 3000 .mu.m or less in the satin net.
The grey fabric of the elastic warp knitted fabric has other problems. One being that the grey fabric of the knitted fabric has an irregularity between a density in a central portion of the warp knitted fabric and a density in a portion near to a selvage of the warp knitted fabric. This irregularity is generated because the grey fabric is wound in a state such that a strain generated in the grey fabric during a knitting operation is maintained in a rolled fabric, a surface of the warp knitted fabric is made flat by a pressure applied to the warp knitted fabric during the winding operation, and there is a difference of the pressure between the center portion and the portion near to the selvage of the warp knitted fabric. Accordingly, a difference of the pressure between the center portion and the portion near to the selvage of the warp knitted fabric causes an irregularity of a density between the center portion and the portion near to the salvage of the warp knitted fabric. And then the balance between the wale elongation and the course elongation becomes irregular between the center portion and the portion near to the selvage of the warp knitted fabric.
Another problem is that the elastic yarn in the grey fabric is not tightly held in a knitted weave of the warp knitted fabric, because the nonelastic yarn is not shrunk in the grey fabric which is not applied with a dyeing and finishing process, and the nonelastic yarn cannot apply a tightening force on the elastic yarn. Accordingly, when a stretching and shrinking operation is repeated on the warp knitted fabric, the elastic yarn is likely to move in the grey fabric of the warp knitted fabric, and thus a fabric distortion caused by a dislocation of the elastic yarn from the original position may be generated.
Japanese Technical Magazine "Process Technique" Vol. 23, No. 6 (1989), page 379 to 385 discloses a technique using an air flow dyeing machine, and that a warp knitted fabric of a polyamide yarn and a polyurethane elastomer yarn is dyed by the air flow dyeing machine, but this reference does not disclose in detail a structure of the warp knitted fabric, conditions of treatment applied to the warp knitted fabric, and an effect caused by this treatment.
The inventors of the present application took note of a bulge of a sinker loop formed by a nonelastic yarn in the grey fabric, and carried out intensive research to obtain a warp knitted fabric in which the bulge of the nonelastic yarn is kept as much as possible, an irregularity of a balance between a wale elongation and a course elongation is made as small as possible, and a fabric distortion is alleviated, and thus found that a warp knitted fabric having a stretchable quality in a course direction, and a superior balance between the wale elongation and the course elongation, can be obtained by applying a specific bulge to a sinker loop of the nonelastic yarn.